Systems and methods for using polyaxial plates

ABSTRACT

Certain embodiments of the invention provide plates for treating periarticular fractures or other non-full body weight bearing applications that combine polyaxial fixation with a low profile and enhanced contouring that more closely conforms to bone. Such plates can be designed to achieve buttressing effect and/or to be used in a reinforcement mode. Other features can be combined with these. Such plates can be created for use on bone sites such as on a tibia, fibula, metatarsal, calcaneous, other foot bone, humerus, radius, ulna, spinal, maxillofacial, as well as sites on other bones.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/970,779, filed May 3, 2018, which is a continuation of U.S. patentapplication Ser. No. 15/706,877, filed on Sep. 18, 2017, now U.S. Pat.No. 10,092,337, which is a continuation of U.S. patent application Ser.No. 14/535,573, filed on Nov. 7, 2014, now U.S. Pat. No. 9,795,424,which is a continuation of U.S. patent application Ser. No. 13/774,721,filed on Feb. 22, 2013, now U.S. Pat. No. 8,888,824, which is acontinuation of U.S. patent application Ser. No. 12/069,331, filed onFeb. 8, 2008, now U.S. Pat. No. 8,382,807, which is acontinuation-in-part of U.S. patent application Ser. No. 11/996,795,filed on Aug. 1, 2008, now U.S. Pat. No. 8,940,028, which is the U.S.National Phase of International Application No. PCT/US2006/028778 filedon Jul. 25, 2006, which claims the benefit of U.S. ProvisionalApplication Ser. No. 60/702,231, filed on Jul. 25, 2005, titled “LockingScrew,” the entire contents of the prior applications are herebyincorporated by reference in their entirety.

BACKGROUND

This invention relates generally to orthopedic fixation devices and boneplating systems for fracture fixation, and particularly to systems andmethods for using bone plates that provide polyaxial fixation offasteners.

Bone fractures are often repaired by securing a bone plate across thefracture. Depending upon which bone is to be treated, the bone plate maybe straight or curved to match the contour of the bone for which it isdesigned. Bone plates may also be provided in many shapes and sizes. Incases where a bone is severely comminuted or if bone segments aremissing, the use of bone plate and screw systems promotes healing of thefracture by providing a rigid fixation or support structure between thebone and the plate.

Bone plates may be secured to the bone in a number of ways. An existingsolution is a plate and screw system where the screws are locked in theplate. A bone screw is threaded through an opening in the plate and intothe bone. The screw is then secured to the bone plate via threads in thescrew head that cooperate with threaded openings in the bone plate. Thissecures the plate with respect to the bone and provides rigid fixationbecause the relationship between the plate and screw(s) is fixed.Because the head of the locking screw interdigitates with threads in theplate, the plate and screws(s) form a stable system or construct, andthe stability of the fracture can be dependent on or aided by thestiffness of the construct. Locking a screw into the plate can achieveangular and axial stability and eliminate the possibility for the screwto toggle, slide, or be dislodged, reducing the risk of postoperativeloss of reduction.

However, although locking screws may reduce the incidence of loosening,they provide only one fixed angle relationship between the plate and thescrew(s). The insertion angle is limited to a single direction becausethe threads of the head cooperate or mate with the threads of the holein one direction only. The longitudinal axis of the screw lines up withthe central axis of the hole, and no angular variation is allowed. Inshort, locking screws are unidirectional, limiting their use in someinstances.

For example, when treating a severe fracture, fragments may be shatteredand in irregular positions. Although a surgeon may wish to obtain thebenefits of a locking screw and bone plate used together, the angle atwhich the locking screw extends from the plate at a certain opening maynot be the angle that would allow the surgeon to “grab” (or seize, fix,or otherwise secure) the desired, random bone fragment. In this case,the surgeon may need to secure the plate to the bone somewhere else, oruse a non-locking screw. Although non-locking screws do not lock intothe plate, they can be inserted at various angles.

Specifically, non-locking screws are secured into bone in the same waythat locking screws are, but they are not secured to the plate. Theirheads are typically rounded where they contact the bone plate. Thus, oneadvantage of non-locking screws is that they can be inserted at variousangles because they are not limited by the thread-to-thread contact oflocking screws with the bone plate. However, if the surgeon desires therigid stable construct of a locking screw and plate, the use of anon-locking screw to obtain the desired angular orientation is notnecessarily optimal.

There have been bone plating systems developed that provide the surgeonwith the option of choosing a non-locking or a locking screw. In someembodiments, these systems provide plates with some threaded holes (thatmay receive with either locking screws or non-locking screws) and somenon-threaded holes (for non-locking screws). There are also systems thatprovide partially threaded slots to allow either non-locking or lockingscrews to be used together. Such combination slots provide surgeons withthe intraoperative choice about whether to use the plate with lockingscrews, non-locking screws, or with a combination of both. Thesecombination slots typically have a partially threaded opening that canreceive either a compression screw or a locking screw. However, becausethese combination slots are only partially threaded, the lockingscrew(s) may not be able to maintain the fixed angular relationshipbetween the screw(s) and plate under physiological loads. Specifically,the locking screws within the plate are only partially captured and thusonly partially surrounded by threads. Under high stress and loadingconditions, the slot may distort and allow the fixed angularrelationship between the locking screw and plate to change. This canresult in loss of fixation or loss of established intraoperative plateorientation. Moreover, the locking screw can still only be inserted at asingle angle—the predetermined angle defined by the manufacturer.

Additionally, current bone plate and screw systems still limit asurgeon's ability to both (a) lock a fastener with respect to the boneplate, but still (b) allow the fastener to extend from the bone plate atvarious angles. Locking screws lock into the plate, but only in a singleangular configuration, and non-locking screws allow various angleconfigurations, but they do not provide a stable construct with theplate. Accordingly, none of these options allow a surgeon to capturebone fragments that do not fall in line with the axis of the openingprovided on the plate in a rigid fashion. An example of this problem isshown in FIG. 21. Thus, currently available options can still lead tomalalignment and poor clinical results.

There have, however, been some attempts to provide polyaxial lockingsystems. For example, one effort includes providing holes that acceptfixed angle locking pegs and multidirectional locking pegs, with athreaded cap inserted over the multidirectional peg to hold it intoplace. Such a system can be cumbersome to use because although themultidirectional peg can be inserted at any angle, the surgeon thenneeds to thread a small cap onto the top of the peg head and into theplate, requiring an extra step, extra time, and extra instrumentation.Such systems also fail to allow the use of non-locking members inconjunction with the locking and multidirectional pegs.

Other systems that have attempted to offer polyaxial fixation includeproviding a bone plate with inserts at the hole peripheries made out ofa deformable material, with the remaining part of the plate made oftitanium. The plate is manufactured and the inserts are then pushed intothe hole peripheries and engaged in place by deformation and pressure.When screws are inserted, the inserts deform and are compressed betweenthe edges of the holes of the plate, which holds the screws and insertsin place. Challenges with such systems are that they cannot be used withnon-locking screws, the inserts do not have the strength to receive andhold a regular locking screw, (i.e., they do not provide the surgeonwith options), and plates with deformable inserts are more expensive tomanufacture than regular bone plates. Other attempts have failed toprovide adequate locking mechanisms.

Another attempt at polyaxial fixation includes a plate with holes thathave an internal jacket with recesses that extend away from the axis ofthe hole or into the internal jacket surface. This attempt is describedin International Application WO 2005/018472, titled Bone Plate. Theinternal jacket surface of the plate described in that application isthreaded or has ribs or protuberances. A bone screw is intended to bepulled into the hole of the plate by the internal jacket surface. If thebone screw head is threaded, when the screw in inclined, the threadedhead is intended to “jump over” the pitches of the threads in the holeof the plate interrupted by the recesses, without “cutting through”them. The goal of the invention is to provide a bone plate that can havebone screws introduced at an angle that is different from the specifiedaxis of the hole and secured into position.

It would be beneficial to provide plates and methods that combinepolyaxial locking fixation with a thinner profile and enhanced bonecontouring. Such plates could be useful in fixation of partial articularand/or non full body weight bearing fractures, where a more flexibleplate that is more closely shaped in accordance with bone structure andthat features polyaxial locking openings could provide additionaloptions for the surgeon. Such features could, if desired, but notnecessarily, provide plates that allow compression of a mid portionagainst bone to create a buttress effect while other portions of theplate are locked to the bone using polyaxial fixation. Such plates couldalso be used without buttressing effects, but in a more conventionalreinforcement mode. Other features could be combined with any or all ofthese features.

SUMMARY

Certain embodiments of the invention provide plates for periarticularfractures or other non full body weight bearing applications thatcombine polyaxial fixation with a thinner profile and contouring thatmore closely conforms to bone. Such plates can be designed to achievebuttressing effect and/or to be used in a reinforcement mode. Otherfeatures can be combined with these. Such plates can be created for useon portions of the tibia, fibula, metatarsals, calcaneous, other ankleand foot bones, humerus, radius, ulna, spinal, maxillofacial, and otherbones.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a bone plate having fins according toone embodiment of the invention with a fastener inserted therein.

FIG. 2 shows a top perspective view of an opening in a bone plateaccording to one embodiment of the invention.

FIG. 3 shows a top view of a bone plate having multiple openings, with afastener inserted therein.

FIG. 4 shows an underneath view of the bone plate of FIG. 3.

FIG. 5 shows a side perspective view of a bone plate with fastenersinserted therein to illustrate a few of the multiple angles at which theplate can receive a fastener.

FIG. 6 shows an example of a fastener for use with various bone platesdescribed herein.

FIG. 7 shows a top plan view of an alternate embodiment of an opening ina bone plate.

FIG. 8 shows a perspective view of the bone plate of FIG. 7.

FIG. 9 shows a top plan view of a further embodiment of an opening in abone plate.

FIG. 10 shows a perspective view of the bone plate of FIG. 9.

FIGS. 11-15 show alternate shapes and types of bone plates that may beused with various embodiments of this invention.

FIG. 16 shows a cross-section view of an alternate embodiment having afinned fastener in place in a bone plate.

FIG. 17 shows a side perspective view of a fastener having a finned headaccording to one embodiment of the invention.

FIG. 18 shows a top perspective view of the fastener of FIG. 17.

FIG. 19 shows a top perspective view of a bone plate that may be used toreceive the fastener of FIGS. 17 and 18.

FIG. 20 shows a cross-section of the threads of the plate of FIG. 19.

FIG. 21a shows an example of a fracture that may be treated with variousembodiments of the invention.

FIG. 21b is a schematic diagram that shows aspects of a buttressingeffect achieved by certain plates according to certain embodiments ofthe invention.

FIGS. 22a and 22b are schematic drawings which show types of fracturesthat can be treated with plates according to certain embodiments of theinvention.

FIG. 23 is a posterior view of a portion of a tibia and fibula with aninstalled lateral distal fibula plate according to one embodiment of theinvention.

FIGS. 24a and 24b are radiographs showing an installed plate accordingto FIG. 23 and the bone in which it is installed.

FIG. 25a is a top view of the plate of FIG. 23.

FIGS. 25b and c are a top plan view and a cross sectional view,respectively, of a tabbed opening according to one embodiment of theinvention, as found for example in the plate of FIG. 23.

FIG. 26 is a bottom view of the plate of FIG. 23.

FIG. 27 is a left-side elevational view of the plate of FIG. 23.

FIG. 28 is a right-side elevational view of the plate of FIG. 23.

FIG. 29 is a head-end view of the plate of FIG. 23.

FIG. 30 is a shaft end-view of the plate of FIG. 23.

FIG. 31 is a lateral view of portions of a tibia and fibula with aninstalled posterolateral distal fibula plate according to an embodimentof the invention.

FIGS. 32a and 32b are radiographs of an installed plate of FIG. 31 andthe bone in which it is installed.

FIG. 33 is a top view of the plate of FIG. 31.

FIG. 34 is a bottom view of the plate of FIG. 31.

FIG. 35 is a right-side elevational view of the plate of FIG. 31.

FIG. 36 is a left-side elevational view of the plate of FIG. 31.

FIG. 37 is a head-end view of the plate of FIG. 31.

FIG. 38 is a shaft-end view of the plate of FIG. 31.

FIG. 39 is a posterior view of portions of a tibia and fibula with aninstalled lateral proximal tibia plate according to one embodiment ofthe invention.

FIG. 40 is a posterior view of portions of a tibia with a lateralproximal tibial guide according to one embodiment of the invention.

FIGS. 41a and 41b are radiographs showing an installed plate of FIG. 39and the bone in which it is installed.

FIG. 42 is a top view of the plate of FIG. 39.

FIG. 43 is a bottom view of the plate of FIG. 39.

FIG. 44 is a left-side elevational view of the plate of FIG. 39.

FIG. 45 is a right-side elevational view of the plate of FIG. 39.

FIG. 46 is a head-end view of the plate of FIG. 39.

FIG. 47 is a shaft-end view of the plate of FIG. 39.

FIG. 48 is a medial view of portions of a tibia with an installedposteromedial proximal tibial plate according to one embodiment of theinvention.

FIGS. 49a and 49b are radiographs of the plate of FIG. 48 and the bonein which it is installed.

FIG. 50 is a top view of the plate of FIG. 48.

FIG. 51 is a bottom view of the plate of FIG. 48.

FIG. 52 is a left-side elevational view of the plate of FIG. 48.

FIG. 53 is a right-side elevational view of the plate of FIG. 48.

FIG. 54 is a head-end view of the plate of FIG. 48.

FIG. 55 is a shaft-end view of the plate of FIG. 48.

FIG. 56 is a view of portions of a tibia and fibula with an installedmedial distal tibia plate according to one embodiment of the invention.

FIG. 57 is a top view of the plate of FIG. 56.

FIG. 58 is a bottom view of the plate of FIG. 56.

FIG. 59 is a left-side elevational view of the plate of FIG. 56.

FIG. 60 is a right-side elevational view of the plate of FIG. 56.

FIG. 61 is a head-end view of the plate of FIG. 56.

FIG. 62 is a shaft-end view of the plate of FIG. 56.

FIG. 63 is an anterior view of a portion of a tibia with an installedanterior distal tibial plate according to one embodiment of theinvention.

FIG. 64 is an anterior view of a portion of a tibia with an anteriordistal tibial guide according to one embodiment of the invention.

FIGS. 65a and 65b are radiographs of the anterior distal tibia plate ofFIG. 63 and the bone in which it is installed.

FIG. 66 is a top view of the plate of FIG. 63.

FIG. 67 is a bottom-view of the plate of FIG. 63.

FIG. 68 is a right-side elevational view of the plate of FIG. 63.

FIG. 69 is a left-side elevational view of the plate of FIG. 63.

FIG. 70 is a head-end view of the plate of FIG. 63.

FIG. 71 is a shaft-end view of the plate of FIG. 63.

FIG. 72 is a medial view of a portion of a tibia with an installedposterior distal tibia plate according to one embodiment of theinvention.

FIG. 73 is a top view of the plate of FIG. 72.

FIG. 74 is a bottom view of the plate of FIG. 72.

FIG. 75 is a right-side elevational view of the plate of FIG. 72.

FIG. 76 is a left-side elevational view of the plate of FIG. 72.

FIG. 77 is a head-end view of the plate of FIG. 72.

FIG. 78 is a shaft-end view of the plate of FIG. 72.

FIG. 79 is a top view of a tubular plate according to one embodiment ofthe invention.

FIG. 80 is a bottom view of the plate of FIG. 79.

FIG. 81 is a left-side elevational view of the plate of FIG. 79.

FIG. 82 is a right-side elevational view of the plate of FIG. 79.

FIG. 83 is a head-end view of the plate of FIG. 79.

FIG. 84 is a shaft-end view of the plate of FIG. 79.

FIGS. 85a and b are views of low profile lateral proximal tibial platesaccording to one embodiment of the invention with slots or elongatedopenings.

FIG. 86 is a view of a low profile spine plate according to oneembodiment of the invention.

FIG. 87 is a view of a low profile plate according to one embodiment ofthe invention that has multiple types of openings.

FIGS. 88a and b are views of low profile plates according to oneembodiment of the invention that have a slot or elongated opening in theshaft.

FIGS. 89a, b and c are views of partial low profil—partial physiologicalload bearing plates according to one embodiment of the invention.

DETAILED DESCRIPTION I. Plates with Polyaxial Openings Generally

Embodiments of the present invention provide a bone fixation assemblythat can accept and fix fasteners at a plurality of angles. A specificembodiment of a bone fixation assembly 10 is shown as a bone plate 12and fastener 80 in FIG. 1. As shown in more detail in FIGS. 2-4, boneplate 12 has a lower surface 14 and an upper surface 16 and one or moreopenings 18 that extend from the lower surface 14 to the upper surface16.

The embodiments described herein may be used in connection with any typeof bone plate, non-limiting examples of which are shown in FIGS. 11-15.Plate 12 may be adapted to contact one or more of a femur, a distaltibia, a proximal tibia, a proximal humerus, a distal humerus, aclavicle, a fibula, an ulna, a radius, bones of the foot, or bones ofthe hand. The bone plate may be curved, contoured, straight, or flat. Itmay be a periarticular plate or a straight plate. An example of astraight plate in shown in FIG. 11. Plate may have a head portion thatis contoured to match a particular bone surface, such as a metaphysis ordiaphysis, flares out from the shaft portion, that forms an L-shape,T-shape, Y-shape, with the shaft portion, or that forms any otherappropriate shape to fit the bone to be treated. An example of aT-shaped plate is shown in FIGS. 12-15, the openings on the plates inthose figures are described in more detail below.

Bone plate 12 may be comprised of titanium, stainless steel, cobaltchrome, carbon composite, plastic or polymer—such aspolyetheretherketone (PEEK), polyethylene, ultra high molecular weightpolyethylene (UHMWPE), resorbable polylactic acid (PLA), polyglycolicacid (PGA), combinations or alloys of such materials or any otherappropriate material that has sufficient strength to be secured to andhold bone, while also having sufficient biocompatibility to be implantedinto a body. Although the above list of materials includes many typicalmaterials out of which bone plates are made, it should be understoodthat bone plates comprised of any appropriate material are within thescope of this invention.

Opening 18 of plate 12 is shown having a central axis 20, and it isadapted to receive a fastener. The fastener may be any typical, standardlocking fastener or a non-locking fastener, although the embodimentsdescribed herein are intended for particular use with locking fastenersthat have a series of threads on their heads. FIGS. 5-6 show examples offastener 80 that may be used in accordance with embodiments of thisinvention. As shown specifically in FIG. 6, fastener 80 has a shaft 82and a head 84. Shaft 82 may be threaded or otherwise configured toengage bone. It may be fully threaded, partially threaded, comprise ahelical blade, and/or may comprise one or more tacks, deployable talons,expanding elements, or so forth. Any feature that allows shaft 82 toengage bone is considered within the scope of this invention and may bereferred to generally as a “threaded shaft” for the sake of convenience.It is also possible, however, that shaft 82 is not threaded, so thatfastener 80 takes the form of a peg or a pin. This alternativeembodiment may be preferred in certain procedures where, for instance,the main goal is to prevent tilting of a bone segment, or in procedureswhere there is no concern of fastener 80 pulling out from the bone andhence no need for shaft 82 to be threaded or otherwise configured toengage bone. For the sake of reference, shaft 82 is also shown having alongitudinal axis 86. The end of shaft 82 may be a self-tapping orself-drilling tip, as shown in more detail in FIG. 5.

The head 84 of fastener 80 preferably has at least one set of threads88. Threads 88 are typically any standard-type thread. For example, thethreads 88 may be a continuous ridge or a non-continuous ridge. It maycomprise a portion of a revolution, one complete revolution, multiplerevolutions, a single lead, or multiple leads, or any other threadsknown in the art. Additionally or alternatively, head 84 of fastener 80may include any other surface that will engage with and seat withinspecific features of plate (described further below). For example, head84 may have a series of dimples, ridges, bumps, textured areas, or anyother surface that can secure fastener 80 as described herein. As willbe described in more detail below, threads 88 of head are adapted toengage, associate with, or otherwise cooperate with fins 24 of opening18. In short, any type of threaded fastener head is intended for usewith various embodiments of this invention.

Referring to FIG. 2, it can be seen that the embodiment shown has anopening 18 with an inner surface 22 that is defined by a series ofconcavely indented, inwardly protruding fins 24. Fins 24 extend intoopening 18 toward central axis 20. The bases 26 of fins 24 form aconcave portion 28 at or near a round circumference 30 of upper surface16. (The term “round” circumference is intended to refer to any roundshape, such as a circle, an oval, an egg-shaped circumference, or anyother opening shaped to receive the head of a fastener 80.) The bases 26of the fins 24 may all meet in substantially the same plane and thenangle downwardly and inwardly at a similar angle or slope.

It bears noting that the concave portion 28 is smooth and non-threaded.In fact, there are not any threads on concave portion 28 or anywhere oninner surface 22 of opening 18. The lack of threads helps ease themanufacturing of plate 12, and allows plate be manufactured as thinly asdesired.

For example, the thickness of plate 12 and the dimensions of fins 24 aretypically dependent upon the pitch and threads of fastener 80. Forexample, a larger plate 12 for use with a larger fastener (e.g., for useon a femur bone) will likely be thicker and will have larger and thickerfins than a smaller plate (e.g., for use on a smaller bone). In specificembodiments, the fins 24 are particularly thin so that they can be movedup or down and deformed upon pressure. In some embodiments, the fins maybe pressed toward the edges of the plate opening. A non-limitingexemplary range of thicknesses for fins may be from about 0.5 mm toabout 5 mm, although larger and smaller sizes are possible. In theory,the fins 24 are intended to fit between crimps on the threadform offastener 80, as shown in FIG. 1.

Providing a non-threaded inner surface 22 also allows the fastener 80 tobe inserted into opening 18 at any desired angle, because there are notany threads to interfere with the desired angle, as illustrated by FIG.5. The fins 24 are intended to slightly bend, deflect or deform in orderto secure the fastener 80 in place in opening 18. Fins 24 actuallyengage threads 88 or other surface of fastener 10.

Referring back to FIG. 2, in the embodiment shown, as fins 24 extendtoward central axis 20, they taper to form tapered sides 32. The finsend at rounded tip 34, although tips 34 can be pointed, square,rectangular, or any other appropriate configuration. For example, asshown in FIGS. 7 and 8, fins 24 may have straight edges or sides 42 andstraight ends 44. This embodiment shows fins 24 that are partiallyrectangular-shaped. The openings 46 between fins 24 are slit-shaped.

An alternate embodiment is shown in FIGS. 9 and 10, which illustratefins 24 with a more triangular shape. In this embodiment, fins 24 areshown having sides 52 that taper inwardly and edges 54 that are flat andsmall, forming the apex area 56 where sides 52 come to an end. Openings58 between fins 24 are more elongated than openings 46. Both sets ofopenings 46, 58 in these alternate embodiments are shown having roundedbacks 60, where they meet inner surface 22 of opening 18. It should beunderstood however, that these are merely examples of fin 24 shapes andopenings 46, 58 and that any appropriate shapes are possible andconsidered within the scope of this invention. Non-limiting examplesinclude trapezoidal, square, round, circular, triangular (with a pointedtip instead of apex area 56), and any other possible option.

As shown in FIG. 4, a second circumference 36 at the lower or underneathsurface 14 of plate 12 may appear to be more jagged than the roundcircumference 30 at the upper surface 16 due to the fins 24 forming aportion of lower surface 14. The circumference can appear almost“flower-like”—each fin 24 appears to form a petal of the circumference.Alternatively, for the embodiments of FIGS. 7-10, the secondcircumference will appear similar to the shape created by fins 24.

Although the figures show an opening 18 with about five to eight fins24, it should be understood that any number of fins 24 is consideredwithin the scope of this invention. For example, there may be two orthree fins, or ten or twenty or more fins 24, depending upon the platefor which the opening 18 is intended for use.

The primary purpose of fins 24 is to grasp one or more threads 88 of athreaded head fastener in order to secure the fastener in place in thebone plate 12, but a desired angle. For example, as opposed to threadedopenings (which engage the threads of the head of the fastener in oneway only, limiting the surgeon's ability to angle the fastener asdesired), the fins 24 of this embodiment are still intended to securethe threads of the head of fastener in place, but at any angle. As thefastener is inserted, its threads start to engage the fins 24, as shownin FIG. 1. As discussed above, the fins 24 may be very thin so that asthe head threads 88 start to grab fins 24, the fins 24 may move up ordown as appropriate to engage the threads 88 and secure the fastener 80.In short, the threads 88 engage fins 24 (or fit in between fins 24). Inmost cases, this movement of fins 24 is a permanent deformation, so thatthe fins cannot flex back and allow the fastener to work its way out.

As discussed above, finned openings 18 may be provided on all types ofbone plates, examples of which are shown in FIGS. 11-15. FIG. 11 shows aspecific example of an opening 18 with fins 24 (referred to as a finnedopening 18), a smooth opening 60, a threaded opening 62, and aprovisional pin opening 64. Other options are holes that can be usedwith either a threaded or non-threaded fastener, as well as combinationslots. It should be understood that these various types of openings maybe used on any types of bone plates, in any combination and in any size,examples of which are shown in FIGS. 12-15. FIG. 12 shows a plurality offinned openings 18 in the head 70 of bone plate 12. This may helpachieve better fixation of a fractured bone, because the fastener can beinserted at various angles to capture “renegade” or random bonefragments that have split from the bone during fracture, but stillsecure the bone fragments to the plate. For example, if a wrist bone isbroken, there will be numerous fragments that may shatter in variousdirections. The plates 12 with finned openings 18 described herein canbe used to place a fastener 80—at various angles in order to capture therenegade fragments that would otherwise not be secured to a bone plateusing only a locking or a non-locking fastener. It should additionallybe understood that other types of openings (in addition to or instead offinned openings 18) may be present in the head 70, as well as elsewhereon plate 12.

As previously mentioned, fastener 80 may be any typical fastener, madeout of any appropriate material. It will typically have a bore forreceiving a driver in order to secure fastener into bone and into plate12. The receiving bore may be any size and shape, for example, it mayhave a hexagonal configuration to receive a corresponding hexagonaldriver, a Phillips screw head, a flat-head, a star configuration, Torx,or any other appropriate configuration that can cooperate with a driverto place fastener.

Turning now to the methods of implantation, the surgeon accesses thesurgical site of interest, which can be an internal site at which a bonefracture is located that requires stabilization to ensure properhealing. The fracture may be reduced with conventional forceps andguides (which are known to those in the art), and a bone plate ofappropriate size and shape is placed over the fracture site. In someinstances, the bone plate may be temporarily secured to the bone usingprovisional fixation pins. In the bone plates shown in FIGS. 11 and 12,provisional fixation pins may be used through either the provisional pinopenings, or any other opening (threaded or non-threaded or finned) inthe plate. Provisional fixation provides for temporarily securing thebone plate to the bone before placing fixation screws through the boneplate, so that one can be certain the bone plate is properly positionedbefore placing bone screws for permanent fixation of the bone plate tothe bone. Moreover, with provisional fixation, x-rays can be taken ofthe bone plate/construct without excess instruments in the field ofview.

Once the plate 12 is secured at a desired location in relation to thefracture (typically using one or more provisional fixation pins,although any other appropriate method may be used), the surgeon thenidentifies an insertion angle, or the direction along which fastener 80is to be inserted through a selected opening 18 and driven into bonematerial. If bone plate 12 includes more than one opening, as shown inthe figures, the surgeon also selects the specific opening to be used.After selecting the desired insertion angle and opening, the surgeoninserts shaft fastener 80 through opening 18 until the tip contacts bonematerial. In some cases, a hole may need to be drilled or tapped intothe bone along the insertion angle to facilitate the initial tapping orinsertion of fastener 80. The surgeon then uses an appropriate drivingtool in the receiving bore of head 84 to manipulate the fastener 80 intoplace.

Because fastener 10 may be inserted at angles other than the alignedwith the central axis 20 of the opening 18, as shown in FIG. 5, fastener80 may be used to grab or secure bone fragments that are out of linewith the traditional angle at which a locking screw would normally beinserted. The surgeon may need to toggle or maneuver the fastener 80 inorder to secure and draw in displaced bone fragments.

Once the bone fragment is secured, the fastener 80 is ready to besecured to the plate 12. As fastener 80 is driven further into bone, itis also drawn further into plate 12. As threads 88 of fastener head 84begin to contact fins 24, the fins are allowed to engage within thethreads to hold the fastener 80 in place in the desired angle, evenangles that are other than in line with the central axis 20. The actionof engagement between fins 24 and threads 88 rigidly affixes fastener 80to the bone plate 12 at the desired insertion angle. In someembodiments, the surgeon may then use traditional locking and/ornon-locking screws in other openings on plate. This can help furthersecure the bone plate to the bone fracture if needed. One advantage ofopening 18 is that it is adapted to receive any one of the potentialfasteners that may be used with plate 12.

In some instances, once all fasteners and/or screws are placed, thesurgeon may place covers over the unused openings, particularly if thereare any unused openings that cross the fracture in order to strengthenthe plate 12. Additionally or alternatively, the surgeon may use bonegraft material, bone cement, bone void filler, and any other material tohelp heal the bone.

An alternate embodiment of a fixation assembly is shown in FIGS. 16-18.These figures show a fastener 102 with a finned head 104. Specifically,the finned head 104 comprises a receiving bore 106 at its upper portion108 and at least one set of extending fins 110 around the main portion112 of the head 104. Fins 110 are shown as being square ortrapezoidally-shaped with tapered edges, although they may be any othershape, such as rounded, oval, rectangular, curved, rhomboid,diamond-shaped, triangular or any other appropriate shape. The edges 111of fins 110 may taper inwardly, outwardly, or be about parallel with oneanother. Fins 110 may be provided in a single row around head 104 orlayered in multiple rows as shown. If layered in multiple rows, eachindividual fin 110 may be directly above another fin (so the top of thefastener 100 looks like that shown in FIG. 18). Alternatively, eachindividual fin 110 in a lower layer may be offset from a fin in a higherlayer. The number of fins 24 in a set may also vary from about two orthree up to any desired number that can fit on main portion 112 of head104. As with the fins 24 of opening 18 described above, the fins 110 arepreferably quite thin, the thickness varying depending upon the use offastener and plate. For example, a larger fastener 102 for use with alarger plate (e.g., for use on a femur bone) will likely have larger andthicker fins 110 than a smaller fastener (e.g., for use on a smallerbone). In specific embodiments, the fins 110 are particularly thin sothat they can be moved up or down or compressed upon pressure. Anon-limiting exemplary range of thicknesses for fins may be from about0.5 mm to about 5 mm, although larger and smaller sizes are possible. Intheory, the fins 110 are intended to fit between the threadform ofplate. Fastener may also have a shaft 114 that is threaded orunthreaded, as described above with respect to fastener 80.

Fastener 102 may be used with any bone plate that has a threadedopening. Any of the examples shown in the figures described above may beused with fastener 102. One option of a specific bone plate that can beused with fastener 110 is shown in FIG. 19. This bone plate 120 has Acmethreads 124 that have a more rectangular shape than the pointed, sharpthreads that are typically used in bone plates. As shown in FIG. 20,opening 122 has threads 124 that end at their edges 126 in a rectangularshape. Providing a rectangular shape with a flatter edge 126 allows alarger channel for the fins 110 to engage. In an even more specificembodiment, the threads 124 may be angled at about 15-20 degrees off ofthe central axis 130 of opening 122, and even more specifically, atabout 18 degrees off of the central axis 130.

An example of the method of use is similar to that describe above. Asfastener 102 is being inserted into bone plate 120 (although it shouldbe understood that any traditional bone plate may used; Acme threads arenot a requirement), the fins 110 are intended to engage threads of theplate and, much like the fins of the bone plate described above, fins110 are very thin so that as the threads of plate 120 start to grab thefins 110, the fins 110 may move up or down as appropriate to engage thethreads of plate and secure the fastener 102 in place, as shown in FIG.16. In most cases, this movement of fins 110 is a permanent deformation,so that the fins cannot flex back and allow the fastener to work its wayout.

II. Low Profile Plates

Generally

FIGS. 23-89 show a number of low profile plates in accordance withcertain embodiments of the invention. In general, such low profileplates can be used to treat partial articular fractures of the distaland proximal tibia such as those shown in FIGS. 22a and 22b andclassified as AO/OTA Fracture classification type B. Such plates canalso be used to treat such fractures in other bones, including, forexample, portions of the metatarsals, calcaneous, other ankle and footbones, humerus, radius, ulna, spinal, maxillofacial, and other bones. Atubular plate as shown in FIGS. 79-84 can be used to treat fractures,nonunions and osteotomies of the medial malleolus, fibula, distal ulna,olecranon, calcaneus, and metatarsals, among other bones.

Certain embodiments of such low profile plates are particularly usefulin connection with periarticular fractures and fractures that do notbear full body weight. They are generally contraindicated for treatmentof AO/OTA fracture classification types A and C, as well as fractureswith extreme metaphyseal, comminution or dissociation of the articularsegment from the bone shaft. Such low profile plates, subject to theselimitations, can also be used in connection with osteopenic bone.

Generally, certain embodiments of such low profile plates can featurethicknesses of approximately 2 mm or less. Other thicknesses arepossible. This thin or low profile acts together with the contouring ofthe plates, any desired edge treatment and screw-head shape to minimizewear of or effect on soft tissue surrounding the installed plates. Thethin profile also acts in combination with the dimensions of the plateto provide a structure that is generally more flexible than conventionalbone plates and thus particularly suitable for low profile, bonecontouring, non-full body weight or physiological load bearing fixationin metaphyseal areas of bones such as, for example without limitation,tibia and fibula.

These structural and material characteristics of some embodiments ofsuch low profile plates can also provide plates which can be applied toachieve a buttress effect, whereby mid portions of the plate arecompressed against bone using one or more cortex, compression orosteopenic screws and thereafter fixation is accomplished with polyaxiallocking screws using polyaxial openings that can accept locking screwspolyaxially. FIG. 21B schematically illustrates aspects of thisbuttressing effect. It shows a plate 175 that is not precisely shapedaccording to bone contour; rather, in one or more areas such as near themidportion of the plate 175, there is a gap between the plate 175 andthe bone. When a compression screw 177 is inserted and torqued into thebone, the screw 177 pulls the plate 175 toward the bone or compressesthe plate 175 on the bone. Flexibility or “springiness” of the plate175, particularly in low profile plates according to certain embodimentsof the invention, causes portions of the plate 175 located more towardthe ends to bear against the bone or bone fragments in such a way thatstabilization of the fracture is enhanced. The buttressing effect isassisted by insertion of locking screws into polyaxial openings of theplate to help create a more integral bone/plate construct for betterstabilization, particularly in periarticular fractures. Certain lowprofile plates according to certain embodiments of the invention can beapplied to bone in a reinforcement mode, rather than the buttress mode.

Low profile plates according to certain embodiments of the invention areparticularly well suited to challenges presented by partial articularfractures. Factors such as intra-articular fracture extension, fracturepattern instability, and inadequate soft tissue coverage are addressedby plates according to certain embodiments of the invention that arepreferably both versatile and comprehensive in their approach tofracture fixation. Traditional locked plating systems can enhancefracture stability through predetermined screw trajectories and preciseplate position on bone. The enhanced stability can, however, reduceintraoperative versatility with respect to plate and screw placement.However, polyaxial locked low profile plates according to certainembodiments of the invention offer a greater degree of freedom relativeto final implant position in connection with partial articular fracturesand other fractures. According to certain embodiments, locking screwsthat feature heads with threads on their periphery, such as for example,conventional locking screws, can be inserted and retained in polyaxialopenings in the plate up to 15 degrees in any direction and require noadditional implants or procedural steps to ensure definitive locking.Low profile fixation in areas where implant prominence is a chiefconcern is accomplished by minimizing plate thickness near the jointwithout compromising needed implant strength, and minimizing screw headprotrusion beyond the plate exterior surface in a way that wouldirritate surrounding tissue.

Accordingly, low profile plates according to certain embodiments of theinvention take advantage of three features:

-   -   (1) Polyaxial locking;    -   (2) Low profile; and    -   (3) Enhanced plate contouring.

According to certain embodiments, tabbed openings include a number ofseparate tabs, preferably but not necessarily five, that engage withthreads of the locking screw head to form a fixed angle construct.Structure of tabs depends on a number of factors including thickness ofplate, desired use of the plate, materials, types of screws contemplatedfor the plate, and other factors. Locking screws can be angled andlocked up to 15 degrees in any direction, allowing for the creation ofcustomized, multi-directional locked plating constructs. Preferably,each opening can accept 3.5 mm cortex, 3.5 mm locking and/or 5.0 mmosteopenia screws. Other types of screws may be used in connection withsuch openings, including other compression, cortex, locking, and/orosteopenia screws. Other types of polyaxial openings can also be used,as disclosed for example in Section I above. Preferably, openings areformed such that a locking screw can be withdrawn and reinserted amultiple number of times, including in different directions, withoutlosing substantial angular retention of the screw by the plate.

The low profile feature ensures low profile fracture fixation in areasof minimal soft tissue coverage such as periarticular zones. Preferably,all screws also have a low head profile further to reduce potential forsoft tissue irritation in these sensitive areas. Preferably, thethickness of such plates is approximately 2 mm or less.

Enhanced plate contouring not only minimizes prominence of the plate andtherefore reduces potential for soft tissue irritation, but alsofacilitates fracture reduction and stabilization by allowing, ifdesired, mid portions of the plates to be compressed to bone to achievebuttressing effect. This effect helps, among other things, to resisttorque and bending during fracture healing. Once securely fixed in placeusing such compression techniques, the plate produces a buttress effectto the fracture site to help prevent loss of reduction and enhanceoverall fracture fixation. Achieving buttressing effect is notnecessary, however; the plates can also be installed in a reinforcementmode. Contouring also allows additional screw convergence in metaphysealareas of bone.

Low profile plates according to certain embodiments of the invention arepreferably made from ASTM F 139 Implantable Stainless Steel material orequivalent. Other suitable materials include titanium, titanium alloy,or any other bio compatible material which allows plates to performsatisfactorily with polyaxial locking, low profile and enhanced platecontouring features of embodiments of the invention. Indentations orundercuts, shown for example with numeral 521 in FIG. 51, can be formedin the interior surfaces of any such plates, including those for thetibia or fibula disclosed below, where desired to increase flexibilityat certain locations; such indentations can be oriented perpendicular tothe length of the plates or as otherwise desired.

Various types of openings can be used in low profile plates according tocertain embodiments of the invention, including embodiments of platesdisclosed below. Such openings can include, for example, tabbed openingsas disclosed below, other polyaxial openings that are intended toreceive and retain a locking screw at multiple angles, conventionalthreaded openings, conventional nonthreaded openings, slots, openings asdisclosed in U.S. Pat. No. Re. 31628 reissued Jul. 10, 1984 to Allgower,et al., and/or openings as disclosed in U.S. Pat. No. 6,322,562 issuedNov. 27, 2001 to Wolter. U.S. Pat. No. Re. 31628 and U.S. Pat. No.6,322,562 are herein incorporated by reference.

Following is a discussion of examples of certain low profile plates thatincorporate these principles and that can be used in areas of the lowerleg. Low profile plates according to embodiments of the invention can beused in other bones, as discussed above, but the following arenonlimiting examples.

Lateral Distal Fibula Plates

FIG. 23 is a posterior view of distal portions of a tibia and fibulawith a lateral distal fibula locking plate according to one embodimentof the invention installed on the fibula. Generally, plate 200 alsocontains a head 214, a generally elongated shaft 216 and a transitionportion 218 which generally connects the head 214 and shaft 216. Plate200 includes an exterior surface 202, a bone contacting or partiallybone contacting interior surface 204, a left edge 206, a right edge 208,a head end 210 and a shaft end 212. Exterior surface 202 may begenerally convex, flat, or shaped as otherwise desired. Interior surface204 may be generally concave, flat, or shaped as otherwise desired.Interior surface 204 can contain one or more indentations or undercutswhich traverse across the interior surface 204 to modify flexibility ofthe plate, reduce bone contact, or other purposes.

Plate 200 is shaped to lie along the lateral aspect of the distal fibulaand includes a cluster of tabbed openings 220 in the head through whichscrews can penetrate portions of the lateral malleolus. The transitionportion 218 angles laterally, or toward the exterior surface 202,proceeding from shaft 216 to head 214. The head 214 is preferably cuppedto conform to portions of the lateral malleolus. The shaft 216 ispreferably shaped according to a traditional ⅓ tubular plateconventionally used to treat fibula fractures. Edges can be rounded andthe shaft end 212 is preferably chamfered to facilitate percutaneousinsertion.

FIGS. 25b and 25c show detail relating to tabbed openings 220 that canbe formed in plate 200. The plan view of FIG. 25b shows a tabbed opening220 containing five tabs 222 and valleys 224. More or fewer tabs 222 canbe used. Tabs 222 can but need not have an extremity 226 which can bebut need not be of constant radius. Similarly, valleys 224 can ifdesired feature a constant radius. In cross section, as shown in FIG.25c , the tabs 222 feature a concave or dished outer surface 228 and aninner surface 230 that can conform to the shape of the interior surface204 of plate 200. Tab outer surfaces 228, as can be appreciated withreference to FIGS. 25b and 25c , together with portions of the opening220 radially outward of valleys 224, form a dished compression screwreceiving surface 232 that can be dished or otherwise formed to receivethe head of a compression, cortex or osteopenic screws, or othersuitable screw that can act to impart compression on a bone plate as itis rotated into the bone. Preferably as shown in FIG. 25c , but notnecessarily, receiving surface 232 features a constant cross sectionalradius. The particular structure shown in FIG. 25c allows opening 220 toreceive and retain or lock relative to the plate in angularity 3.5 mmlocking screws at orientations or angles up to 15 degrees in anydirection from axial. That structure also allows openings 220 to receive3.5 mm cortex and/or 5.0 mm osteopenia screws for compressing midportions of plates according to embodiments of the invention againstbone for buttress effect.

Preferably, the axis 234 of opening 220 is normal to a tangent formed atthe center of the opening to the interior surface 204 of plate 200. Axis234 could also be oriented normal to a tangent at the center of opening220 to exterior surface 202 of the plate. Axis 234 could also be normalto or angulated with respect to either exterior surface 202 or interiorsurface 204 or any other desired structure on plate 200.

Preferably, tab inner surfaces 230 are flush with the interior bonecontacting surface 204 of plate 200. Tab inner surfaces 230 do not needto be flush in that manner, however; they could be planar and/orrecessed from interior bone contacting surface 204 if desired.

In operation, tab extremities 226 engage or cooperate with threads inlocking screws, such as for example by interdigitating with the threads,or inserting themselves between the threads and deflecting, to allow alocking screw to be inserted at a desired angle, and the tabs 222 thento retain the screw at that angle or in that orientation orsubstantially that orientation relative to the plate 200.

Other types of polyaxial openings 220, such those disclosed for examplein Section I above, can also be used for plate 200 in accordance withembodiments of the invention. Additionally, plate 200 can contain othertypes of threaded or nonthreaded openings and/or slots as discussedabove in this document.

FIG. 24b shows a lateral distal fibula plate 200 with a cortex orcompression screw 236 inserted to compress mid portions of plate 200against the fibula to achieve buttressing effect. Two locking screws 238fix the plate 200 to the fibula proximal to the cortex screw 236 andthree locking screws 238 fix portions of plate 200 distal to cortexscrew 236 to portions of the lateral malleolus or distal portions of thefibula. FIGS. 25a and 26-30 show various views of plate 200.

The particular plate 200 shown in FIG. 23 features a thickness of 0.067inches plus or minus 0.005 inches (1.7 mm plus or minus 0.127 mm), butother thicknesses could be used, preferably approximately 2 mm or less.Plate 200 is preferably machined from ASTM F 139 Implantable StainlessSteel material, but other materials as discussed above could be used.Plate 200 is preferably machined from the material, but could bepunched, forged, cast, made according to any combination, or asotherwise desired.

Posterolateral Distal Fibula Plates

FIGS. 31-38 show a posterolateral distal fibula plate according to oneembodiment of the invention. Plate 300 includes an exterior surface 302,a bone contacting or partially bone contacting interior surface 304, aleft edge 306, a right edge 308, a head end 310 and a shaft end 312.Exterior surface 302 may be generally convex, flat, or shaped asotherwise desired. Interior surface 304 may be generally concave, flat,or shaped as otherwise desired. Interior surface 304 can contain one ormore indentations or undercuts which traverse across the interiorsurface 304 to modify flexibility of the plate, reduce bone contact, orother purposes.

Preferably more toward the head end 310 than the shaft end 312, a numberof scallops 314 can be formed in the lateral facing edge of plate 300 asinstalled. A rounded corner 311 can be formed at the right edge 308/headend 310 intersection, and elsewhere as desired. Scallops 314 providespace in which a syndesmotic screw 316 can be inserted without undueinterference by plate 300. Scallops 314 can be any desired shape. Plate300 is otherwise generally in the shape of a ⅓ tubular conventionalfibular plate, with a twist added to the head-end portion 310. The twistis preferably but not necessarily 8 degrees in an axial direction(counterclockwise proceeding toward head end 310 in the plate 300 shownin the drawings). The twist is provided to help avoid the peroneal nervewhen the plate 300 is applied to the fibula.

FIG. 31 shows a compression screw 336 inserted in the third opening 320from distal. Two locking screws 338 are inserted on the distal side ofthe fracture and syndesmotic screw 316. A compression screw 336 isinserted at the proximal end of the plate 300 and two locking screws 338are inserted in the next two openings 320.

Plate 300 preferably features polyaxial openings 320 as disclosed inconnection with openings 220 of plate 200, and a thickness as disclosedin connection with plate 200. It is preferably formed of the materialand by the techniques disclosed in connection with plate 200.Additionally, plate 300 can contain other types of threaded ornonthreaded openings and/or slots as discussed above in this document.

FIG. 32b is a radiograph showing plate 300 applied to bone.

FIGS. 33-38 show various views of the plate 300.

Lateral Proximal Tibia Plates

FIG. 39 is a posterior view of portions of a tibia and fibula with aninstalled lateral proximal tibia plate according to one embodiment ofthe invention. Plate 400 includes an exterior surface 402, a bonecontacting or partially bone contacting interior surface 404, a leftedge 406, a right edge 408, a head end 410, and a shaft end 412.Exterior surface 402 may be generally convex, flat, or shaped asotherwise desired. Interior surface 404 may be generally concave, flat,or shaped as otherwise desired. Interior surface 404 can contain one ormore indentations or undercuts which traverse across the interiorsurface 404 to modify flexibility of the plate, reduce bone contact, orother purposes. The plate 400 is generally “L” shaped, the foot of the“L” forming the head 414 that is ultimately installed adjacent thelateral condyle of the tibia. A transition 418 transitions to a shaft416 that preferably features a chamfered end.

The plate 400 lies along the lateral aspect of the proximal tibia. Afive degree posterior tilt in the transition section 418 aligns opening420 with the contour of the lateral tibial condyle. Plate coverageextending down the shaft 416 is enhanced by imparting a three degreesagittal twist (counterclockwise, proceeding toward head 414 in theplate 400 shown in the drawings) in the plate's proximal segment, whichcan include transition portion 418. Head portion 414 forms a concavitythat conforms to the convexity of the lateral condyle. The head end 414preferably features one or more scallops 422 to accommodate lag orrafter screws that can be used to reinforce the articular surfaces ofthe tibia. Scallops 422, if used, can be formed of any desired shapegenerally to help alleviate interference between plate 400 and the lagscrews. The plate preferably does not conform precisely flush to thediaphyseal/metaphyseal transition of the tibia; the non correspondenceallows compression or mid portions of plate 400 against bone forbuttressing effect.

FIG. 39 shows a compression screw 436 across the fracture, with the head414 receiving three locking screws 438 and the shaft 416 receiving threelocking screws 438 on the other side of the fracture from the head 414.

Provisional openings 424 can be included in head 414 to accept K-wiresor other structure for temporary placement of the plate 400 on bone, forprovisional fixation of bone elements, and/or for visualization of screwtrajectory as desired. Such openings 424 are also potentially useful inconnection with guide 440 shown in FIG. 40 that allows visualization ofplate position and provides a template for independent lag screwplacement relative to scallops 422 of plate 400. K-wires can be insertedthrough the two proximal holes 442 to aid in provisional fixation andfracture reduction, together with such visualization. The guide 440 canbe removed over the K-wires and the plate 400 applied over the K-wiresif desired.

Plate 400 preferably features polyaxial openings 420 as disclosed inconnection with openings 220 of plate 200, and a thickness as disclosedin connection with plate 200. It is preferably formed of the materialand by the techniques disclosed in connection with plate 200.Additionally, plate 400 can contain other types of threaded ornonthreaded openings and/or slots as disclosed in this document.

FIG. 41b is a radiograph of an installed lateral proximal tibia plate400. FIGS. 42-47 show various views of plate 400.

Posteromedial Proximal Tibia Plates

FIG. 48 is a medial view of portions of a tibia with a posteromedialproximal tibia plate according to an embodiment of the inventioninstalled. Plate 500 includes an exterior surface 502, a bone contactingor partially bone contacting interior surface 504, a left edge 506, aright edge 508, a head end 510 and a shaft end 512. Exterior surface 502may be generally convex, flat, or shaped as otherwise desired. Interiorsurface 504 may be generally concave, flat, or shaped as otherwisedesired. Interior surface 504 can contain one or more indentations orundercuts (shown as numeral 521) which traverse across the interiorsurface 504 to modify flexibility of the plate, reduce bone contact, orother purposes. Head 514 generally forms the top of a “T” with respectto shaft 516. A transition portion 518 imparts a posterior angle in planview, or medial angle in side view, proceeding from shaft 516 to head514. Additionally, an axial twist (counterclockwise proceeding to head514 in the plate 500 shown in the drawings) allows the head 514 toconform more closely to the medial condyle. The head 514 forms aconcavity that generally conforms to the convexity of the medialcondyle.

Head end 510 preferably includes scallops 522 for purposes ofaccommodating lag screws as disclosed in connection with plates 400.Plate 500 can also contain provisional openings 524 as disclosed inconnection with plates 400 to accommodate K-wire or other provisionalfixators for purposes of visualization of screw trajectory, provisionalfixation and as otherwise desired. Shaft end 512 preferably features achamfered portion for percutaneous insertion.

FIG. 49b is a radiograph that shows a compression screw 536 insertedthrough an opening 520 across the fracture. Three locking screws 538 areinserted through the head and four locking screws 538 are inserted alongthe shaft. FIGS. 50-55 show various views of plate 500.

Plate 500 preferably features polyaxial openings 520 as disclosed inconnection with openings 220 of plate 200, and a thickness as disclosedin connection with plate 200. It is preferably formed of the materialand by the techniques disclosed in connection with plate 200.Additionally, plate 500 can include other threaded or nonthreadedopenings and/or slots as disclosed in this document.

Medial Distal Tibia Plates

FIG. 56 is an anterior view of distal portions of a tibia and fibulawith a medial distal tibia plate 600 according to an embodiment of theinvention installed. Plate 600 includes an exterior surface 602, a bonecontacting or partially bone contacting interior surface 604, a leftedge 606, a right edge 608, a head end 610 and a shaft end 612. Exteriorsurface 602 may be generally convex, flat, or shaped as otherwisedesired. Interior surface 604 may be generally concave, flat, or shapedas otherwise desired. Interior surface 604 can contain one or moreindentations or undercuts which traverse across the interior surface 604to modify flexibility of the plate, reduce bone contact, or otherpurposes. The shaft 616 transitions to a transition portion 618 whichflares to form a head 614 that is flared and generally cupped toaccommodate portions of the medial malleolus or distal tibia. Theconcavity on the interior surface 604 of head 614 allows openings 620 tobe oriented so that screws 638 can converge in metaphyseal portions ofthe tibia. The distal-most openings 620 are preferably positioned justsuperior to the plafond. The plate 600 features a sagittal twist in atleast the transition portion 618 (clockwise proceeding toward head 614).The openings 620 in head 614 are preferably staggered to allow for agreater concentration of locking screws 638 into the metaphyseal portionof the tibia, and also for those screws to converge for additionalfixation benefits. FIG. 56 shows a compression screw 636 placed acrossthe fracture with locking screws 638 inserted proximal to the fractureand other locking screws 638 through the head 614.

Provisional openings 624 as discussed in connection with plate 400 canbe used. Plate 600 preferably features polyaxial openings 620 asdisclosed in connection with openings 220 of plate 200, and a thicknessas disclosed in connection with plate 200. It is preferably formed ofthe material and by the techniques disclosed in connection with plate200. Additionally, plate 600 can contain other types of threaded ornonthreaded holes and/or slots as disclosed in this document.

FIGS. 57-62 show various views of plate 600 that make more apparent,among other things, the cupped shape of the head 614 and the sagittaltwist.

Anterior Distal Tibia Plates

FIG. 63 shows an anterior view of distal portions of a tibia with ananterior distal tibia plate 700 according to one embodiment of theinvention installed. Plate 700 includes an exterior surface 702, a bonecontacting or partially bone contacting interior surface 704, a leftedge 706, a right edge 708, a head end 710 and a shaft end 712. Exteriorsurface 702 may be generally convex, flat, or shaped as otherwisedesired. Interior surface 704 may be generally concave, flat, or shapedas otherwise desired. Interior surface 704 can contain one or moreindentations or undercuts which traverse across the interior surface 704to modify flexibility of the plate, reduce bone contact, or otherpurposes. The shaft 716 transitions to a transition portion 718 thatangulates anteriorally as does, preferably, head 714, with respect toshaft 716. The transition 718 and head 714 form a delta shape toaccommodate fixation into the metaphyseal portion of distal tibia.Material may be removed or omitted to form windows 740 which can beshaped as desired. Windows 740 can help with respect to bone loss andalso provide additional opportunities for fixation. Head 714 features agenerally concave inner surface 704 to accommodate the general convexshape of the anterior distal tibia. Head end 710 can include one or morescallops 722 that can be formed to allow plate 400 to accommodate orminimally interfere with placement of lag screws or other fixationscrews. Provisional openings 724 can be provided as discussed inconnection with plate 400. Preferably, the shaft end 712 features achamfer for percutaneous insertion.

Plate 700 preferably features polyaxial openings 720 as disclosed inconnection with openings 220 of plate 200, and a thickness as disclosedin connection with plate 200. It is preferably formed of the materialand by the techniques disclosed in connection with plate 200.Additionally, plate 700 can contain other types of threaded ornonthreaded openings and/or slots as disclosed in this document.

FIG. 64 shows an anterior distal tibia positioning guide 742 for useduring installation of plate 700. Guide 742 can feature provisionalopenings 744 and scallops 746 such as the kinds disclosed in connectionwith guide 440 disclosed above. Guide 744 can allow visualization ofplate 700 position and provide a template for independent lag screwplacement in the distal tibia relative to scallops 722 in plate 700.K-wires can be inserted through the two distal provisional holes 744 toaid with provisional fixation and fracture reduction. The guide 742 canbe removed over the K-wires and the selected plate 700 then applied overthem.

FIG. 65b is a radiograph that shows a plate 700 installed on a tibia.FIGS. 66-71 show various views of plate 700.

Posterior Distal Tibia Plates

FIG. 72 is a medial view of a distal portion of a tibia with a posteriordistal tibia plate 800 according to one embodiment of the inventioninstalled. Plate 800 includes an exterior surface 802, a bone contactingor partially bone contacting interior surface 804, a left edge 806, aright edge 808, a head end 810 and a shaft end 812. Exterior surface 802may be generally convex, flat, or shaped as otherwise desired. Interiorsurface 804 may be generally concave, flat, or shaped as otherwisedesired. Interior surface 804 can contain one or more indentations orundercuts which traverse across the interior surface 804 to modifyflexibility of the plate, reduce bone contact, or other purposes. Plate800 is shaped generally to fit the posterior aspect of the distal tibiawith head end 810 resting just superior to the tibial plafond. The shaft816 transitions in transition area 818 to an enlarged head 814, so thatthe transition 818 and the head 814 accommodate three openings 820. Theshaft 816 and transition 818 feature a coronal axial twist(counterclockwise proceeding toward the head in the plate shown in thedrawings) to allow conformance to the bone. The transition portion 818and head 814 also angle posteriorly relative to the shaft 816, as shownin FIG. 72. Plate 800 can include one or more scallops 822, which may beformed as disclosed in connection with plate 400, to accommodate andminimize interference with lag screws in the metaphyseal area of thetibia. Provisional openings 824 can be used as disclosed in connectionwith plate 400.

Plate 800 preferably features polyaxial openings 820 as disclosed inconnection with openings 220 of plate 200, and a thickness as disclosedin connection with plate 200. It is preferably formed of the materialand by the technique disclosed in connection with plate 200.Additionally, plate 800 can contain other types of threaded ornonthreaded openings and/or slots as disclosed in this document.

FIGS. 73-78 show various views of plate 800.

Linear Plates

FIGS. 79-84 show a low profile linear plate 900 in accordance with anembodiment of the invention. Plate 900 includes an exterior surface 902,a bone contacting or partially bone contacting interior surface 904, aleft edge 906, a right edge 908, a first end 910, and another end 912.Exterior surface 902 may be generally convex, flat, or shaped asotherwise desired. Interior surface 904 may be generally concave, flat,or shaped as otherwise desired. Interior surface 904 can contain one ormore indentations or undercuts which traverse across the interiorsurface 904 to modify flexibility of the plate, reduce bone contact, orother purposes. The plate contains multiple tabbed openings 920 each ofwhich can accept a compression or osteopenic screw 936 or a lockingscrew 938. Plate 900 also includes a mid portion 940 without a tabbedopening 920, to accommodate greater bending moments located in this areaof plate 900. Such a plate 900 can be seen installed on bone in theradiograph shown in FIG. 65b . The linear plate can include scallopsalong either or both edges as described above, as well as provisionalholes and indentations on the interior surface, and/or other features asdesired.

Plate 900 preferably features polyaxial openings 920 as disclosed inconnection with openings 220 of plate 200, and a thickness as disclosedin connection with plate 200. It is preferably formed of the materialand by the techniques disclosed in connection with plate 200.Additionally, plate 900 can contain other types of threaded ornonthreaded holes and/or slots as disclosed in this document.

Low Profile Plates with Slotted Head

FIGS. 85a and 85b show a low profile plate 1000 with one or more slots1021 in addition to polyaxial openings 1020 in accordance with anembodiment of this invention. Plate 1000 can be any of the low profileplates disclosed above or any other low profile plate as desired, forany bone, which features the polyaxial openings, low profile andenhanced coutouring features according to embodiments of the invention.FIGS. 85a and 85b show, for purposes of illustration, a modified lateralproximal tibial plate 1000 similar to plate 400, but with a slot orelongated opening in head 1014. Plate 1000 includes an exterior surface1002, a bone contacting or partially bone contacting interior surface1004, a left edge 1006, a right edge 1008, a head end 1010, and a shaftend 1012. Exterior surface 1002 may be generally convex, flat, or shapedas otherwise desired. Interior surface 1004 may be generally concave,flat, or shaped as otherwise desired. Interior surface 1004 can containone or more indentations or undercuts which traverse across the interiorsurface 1004 to modify flexibility of the plate, reduce bone contact, orother purposes. The head 1014 contains, in this particular embodiment,an elongated opening or slot 1021 which can be partially tabbed orotherwise fitted with polyaxial screw retention structure as shown inFIG. 85b or without tabs or such structure as shown in FIG. 85a . Theslot 1021 allows additional flexibility in placement of fixation screws,whether locking in ends of the slot 1021 shown in FIG. 85b , orcompression screws which can be inserted in slots 1021 of either plates1000 shown in FIG. 85a or 85 b. Accordingly, a slot 1021 as shown inFIG. 85b , regardless of which plate it may be used on, can accepteither cortex, compression, osteopenic screws 1036 or locking screws1038. Such a slot 1021 can also be formed in the shaft if desired, asshown in FIGS. 85a and b . Scallops 1022 and/or provisional openings1024 can be included as disclosed above in connection with plate 400.

Plate 1000 preferably features polyaxial openings 1020 as disclosed inconnection with openings 220 of plate 200, and a thickness as disclosedin connection with plate 200. It is preferably formed of the materialand by the technique disclosed in connection with plate 200.

Spinal Low Profile Plates

FIG. 86 shows a low profile spine plate 1100 in accordance with oneembodiment of the invention. Plate 1100 can be shaped like aconventional spine plate and can include an exterior surface 1102, aninterior surface 1104, a left edge 1106, a right edge 1108, a first end1110, and another end 1112. The plate can contain polyaxial openings1120 which can be formed as disclosed in connection with openings 220 ofplates 200. Plate 1100 can have a thickness as disclosed in connectionwith plate 200, or thinner if desired. Plate 1100 can be formed usingmaterials and techniques as disclosed in connection with plate 200.

Uniaxial/Polyaxial Low Profile Plates

FIG. 87 shows a low profile plate 1200 according to another embodimentof the invention. Plate 1200 is generally like that shown in FIG. 12,except that it can be formed with a thickness as disclosed in connectionwith plate 200, it can contain polyaxial openings 1220 as disclosed inconnection with plate 200, and it has enhanced bone contouring inaccordance with embodiments of the invention. Plate 1200 includes anexterior surface 1202, an interior surface 1204, a left edge 1206, aright edge 1208, a first end 1210 and a second end 1212. Exteriorsurface 1202 may be generally convex, flat, or shaped as otherwisedesired. Interior surface 1204 may be generally concave, flat, or shapedas otherwise desired. Interior surface 1204 can contain one or moreindentations or undercuts which traverse across the interior surface1204 to modify flexibility of the plate, reduce bone contact, or otherpurposes. Plate 1200 may be any of the plates disclosed above or anyother desired low profile plate for any bone which features at least onepolyaxial opening 1220 as disclosed above in connection with plate 200,and the low profile and enhanced contouring features of embodiments ofthe invention. Openings 1220 can be formed in the head, shaft, or anyother desired portion of a plate. The plate 1200 can also, if desired,contain one or more conventionally threaded openings 1222 at any desiredlocation, such as where locking functionality is needed but polyaxiallocking functionality is not needed. Plate 1200 can also contain one ormore slots or elongated openings 1224 at any desired location. The slotscan be either partially conventionally threaded or tabbed as disclosedin connection with the slots 1021 of FIGS. 85a and 85b . One or moreprovisional openings 1126 can also be included if desired.Conventionally threaded openings 1222 can accept compression screws,locking screws, or locking pegs as shown in FIG. 12. Plate 1200 can beformed using materials and techniques as disclosed in connection withplate 200.

Low Profile Plates with Slotted Shaft

FIGS. 88a and 88b show low profile plates according to an embodiment ofthe invention that include at least one slot 1321 in the shaft. Plate1300, shown in FIG. 88a , which can take the shape of any of the lowprofile plates disclosed in this document, or other low profile shape asdesired, for any desired bone surface, includes an exterior surface1302, an interior surface 1304, a left edge 1306, a right edge 1308, afirst end 1310, and a second end 1312. Exterior surface 1302 may begenerally convex, flat, or shaped as otherwise desired. Interior surface1304 may be generally concave, flat, or shaped as otherwise desired.Interior surface 1304 can contain one or more indentations or undercutswhich traverse across the interior surface 1304 to modify flexibility ofthe plate, reduce bone contact, or other purposes. Polyaxial openings1320 can be formed as disclosed in connection with openings 220 of plate200. A slot 1321 is included mid plate such as in shaft 1328. The slot1321 allows additional flexibility in fixation, and can be configured asdisclosed in connection with slots 1021 of plate 1000, to accept cortex,compression, osteopenic, locking or other screws.

Plate 1400, shown in FIG. 88b , which can take the shape of any of thelow profile plates disclosed in this document, or other low profileshape as desired, for any desired bone surface, includes an exteriorsurface 1402, an interior surface 1404, a left edge 1406, a right edge1408, a first end 1410, and a second end 1412. Exterior surface 1402 maybe generally convex, flat, or shaped as otherwise desired. Interiorsurface 1404 may be generally concave, flat, or shaped as otherwisedesired. Interior surface 1404 can contain one or more indentations orundercuts which traverse across the interior surface 1404 to modifyflexibility of the plate, reduce bone contact, or other purposes.Polyaxial openings 1420 can be formed as disclosed in connection withopenings 220 of plate 200. A slot 1424 is included mid plate such as inshaft 1428. The slot 1324 allows additional flexibility in fixation, andcan be configured as disclosed in connection with slots 1021 of plate1000, to accept cortex, compression, osteopenic, locking or otherscrews. FIG. 88b shows that a slot 1424 can also be included in a headportion 1430 of the plate 1400. Provisional openings, scallops, andother features can also be included in plates such as plates 1300, 1400,if desired. Plates 1300, 1400 can be formed using materials andtechniques disclosed in connection with plate 200.

Partial Low Profile Polyaxial Plates

FIGS. 89a and 89b show partial low profile/partial load-bearing plates1500 according to an embodiment of the invention. Plate 1500 can beshaped as is conventional for a load-bearing plate for any desired bone,or as otherwise desired. Plate 1500 includes an exterior surface 1502,an interior surface 1504, a left edge 1506, a right edge 1508, a headend 1510, and a shaft end 1512. Exterior surface 1502 may be generallyconvex, flat, or shaped as otherwise desired. Interior surface 1504 maybe generally concave, flat, or shaped as otherwise desired. Interiorsurface 1504 can contain one or more indentations or undercuts whichtraverse across the interior surface 1504 to modify flexibility of theplate, reduce bone contact, or other purposes. Plate 1500 can contain alow profile section 1530 as disclosed in this document, with thicknessas disclosed in connection with plate 200, and polyaxial openings 1520formed as disclosed for openings 220 in plates 200. Any portion of theplate 1500, including low profile section 1530, load-bearing section1532 or both, can include one or more provisional openings 1526.Load-bearing portion 1532 can include, as desired, any combination ofconventionally threaded openings 1522, non-threaded openings 1523, andconventionally non-threaded, partially threaded or partially-polyaxiallylocking structured slots 1524. Slots 1524 can be included in the shaftportion 1534 and/or, if desired, in head 1536. The particular plate 1500shown in FIG. 89a includes in its head 1536 a low profile sectionadapted to accommodate a metaphyseal portion of a bone. A portion of thehead 1536 of plate 1500 of FIG. 89a is shown in cross section in FIG.89c . Plate 1500 shown in FIG. 89b is similar in concept to that shownin FIG. 89a except that the entire head 1536 is formed as a low profileplate in accordance with embodiments of the invention, while the shaft1534 is formed as a load-bearing section. In these plates 1500, theload-bearing sections 1532 and the low profile sections 1530 can bedemarcated as desired to carry out fixation that allows at least part ofthe plate to bear physiologic loads such as body weight and another partof the plate 1500 to operate in accordance with the low profileprinciples disclosed in this document.

Installation of Low Profile Plates

Low profile plates according to certain embodiments of the invention canbe installed as follows. They can be used in connection withintramedullary nails, external fixators and/or other devices, whereinthe nail or other structure absorbs body load, and the plate is usedprimarily to buttress fragments, stabilize the fracture and otherwiseassist in treatment.

A C-arm can be used for fluoroscopy, including preferably arranged toshow the AP plane from lateral positioning. X-rays can be taken ahead oftime and an acetate or other template can be provided that allowsselection of plate and screw sizes. An incision is made and the platecan be inserted percutaneously or as otherwise desired. Fluoroscopy maybe used to ensure that the plate is correctly located. Portions of themetaphyseal area can be opened as desired for reduction of the fracture,access, and other purposes. Wires, forceps and other conventionalinstruments, components, and techniques can be used to restore andreduce the joint. Provisional fixation holes can be used for K-wires toassist in this process, to provisionally fix the plate to bone, to fixbone fragments and perform reduction, and/or to visualize screwtrajectory as desired.

A non-locking screw, such as a cortex, compression or osteopenic screw,can be inserted in one of the openings in the mid portion of the plateto compress that portion against bone to enhance or achieve buttressingeffect. The plate can be installed without such compression to performreinforcement if desired. Drill guides such as those disclosed inPCT/US2007/085210 filed Nov. 20, 2007, which claims priority to U.S.Ser. No. 60/866,665 filed Nov. 21, 2006, both owned by the owner of thisdocument, can be employed as desired. Preferably, two or three holes arefilled with locking screws below the fracture and two or three above,although more or fewer holes can be used. The length or orientation ofscrews can be changed multiple times, such as up to three, with tabbedopenings such as those disclosed above in connection with FIGS. 25b andc . Torque can be applied using conventional torque limiters, which arepreferably set not to exceed 1.7 Newton-meters or 16 inch pounds.Alternatively, locking screws can be hand torqued for final torquing.Wound closure follows conventional technique.

The foregoing description of exemplary embodiments of the invention ispresented for purposes of illustration and description and is notintended to be exhaustive or to limit the invention to the preciseforms, structures or techniques disclosed. Modifications and variationsto those forms, structures and techniques are possible without departingfrom the scope or spirit of the above disclosure and the followingclaims. Alternative embodiments will become apparent to those skilled inthe art to which the present invention pertains without departing fromits spirit and scope.

1. A polyaxial bone fixation system, the system comprising: at least onefastener, the fastener having a head portion and a shaft portion; and abone plate comprising a lower surface, an upper surface and at least oneopening extending from the lower surface to the upper surface; wherein:the at least one opening is adapted and configured to receive the atleast one fastener; and one of the at least one opening and the at leastone fastener includes threads, the other one of the at least one openingand the at least one fastener includes a plurality ofnon-circumferential fins integrally connected to, and protrudingtherefrom, the plurality of non-circumferential fins being arranged andconfigured to move at least a portion of each fin independently towardthe upper surface or toward the lower surface when the at least onefastener is inserted into the at least one opening to secure a positionof the at least one fastener relative to the bone plate at any one of aplurality of angles.
 2. The polyaxial bone fixation assembly of claim 1,wherein the plurality of non-circumferential fins are provided as aseries of concavely indented, inwardly protruding fins that are adaptedto interlock with the threads to secure the head portion of the at leastone fastener relative to the bone plate.
 3. The polyaxial bone fixationassembly of claim 1, wherein the plurality of non-circumferential finsform a concave portion.
 4. The polyaxial bone fixation assembly of claim1, wherein the bone plate has a head portion, the at least one openingbeing located in the head portion of the bone plate.
 5. The polyaxialbone fixation assembly of claim 4, wherein the bone plate furthercomprises one or more of the following: a threaded opening; anon-threaded opening; an opening adapted to receive locking ornon-locking fasteners; an opening with fins; a combination slot; or; anycombination thereof.
 6. The polyaxial bone fixation assembly of claim 1,wherein the plurality of non-circumferential fins are provided in morethan one layer.
 7. The polyaxial bone fixation assembly of claim 1,wherein the plurality of non-circumferential fins includes first andsecond rows of non-circumferential fins, the plurality ofnon-circumferential fins in the first row of fins is offset around acentral axis of the at least one opening relative to the second row ofnon-circumferential fins.
 8. The polyaxial bone fixation assembly ofclaim 7, wherein the first row of non-circumferential fins and thesecond row of non-circumferential fins each include five to eight fins.9. The polyaxial bone fixation assembly of claim 1, wherein theplurality of non-circumferential fins each include inwardly tapered sidesurfaces.
 10. The polyaxial bone fixation assembly of claim 1, whereinthe plurality of non-circumferential fins are arranged and configured todeflect so that each fin is interposed between the threads when the atleast one fastener is inserted into the at least one opening.
 11. Thepolyaxial bone fixation assembly of claim 1, wherein the plurality ofnon-circumferential fins are arranged and configured to deform so thateach fin is interposed between the threads when the at least onefastener is inserted into the at least one opening.
 12. An orthopedicimplant system comprising: an orthopedic implant comprising a first bonecontacting surface, a second surface opposite the first bone contactingsurface, and at least one opening extending from the first bonecontacting surface to the second surface; and at least one fastenerarranged and configured to be inserted into the at least one opening,the at least one fastener having a head portion and a shaft portion;wherein one of the at least one opening and the at least one fastenerincludes threads, the other one of the at least one opening and the atleast one fastener includes a plurality of non-circumferential fins,each fin being arranged and configured to move independently toward thefirst bone contacting surface or the second surface to interlock withthe threads to secure a position of the at least one fastener relativeto the orthopedic implant when the at least one fastener is insertedinto the at least one opening at any one of a plurality of angles. 13.The polyaxial bone fixation assembly of claim 12, wherein the pluralityof non-circumferential fins are provided as a series of concavelyindented, protruding fins.
 14. The polyaxial bone fixation assembly ofclaim 12, wherein the at least one opening includes the plurality ofnon-circumferential fins and the head portion of the fastener includesthe threads, the at least one opening further includes a roundcircumference at the second surface and a jagged circumference formed bythe protruding fins at the bone contacting surface.
 15. The polyaxialbone fixation assembly of claim 12, wherein the at least one openingincludes the plurality of non-circumferential fins and the head portionof the fastener includes the threads, the plurality ofnon-circumferential fins form a concave portion protruding from an innersurface of the at least one opening.
 16. The polyaxial bone fixationassembly of claim 15, wherein the plurality of non-circumferential finseach include a base that meet at the inner surface in substantially thesame plane.
 17. The polyaxial bone fixation assembly of claim 12,wherein the plurality of non-circumferential fins are provided in morethan one layer.
 18. The polyaxial bone fixation assembly of claim 12,wherein the plurality of non-circumferential fins includes first andsecond rows of non-circumferential fins, the plurality ofnon-circumferential fins in the first row of fins is offset around acentral axis of the at least one opening relative to the second row ofnon-circumferential fins.
 19. The polyaxial bone fixation assembly ofclaim 18, wherein the first row of non-circumferential fins and thesecond row of non-circumferential fins each include five to eight fins.20. The polyaxial bone fixation assembly of claim 12, wherein theplurality of non-circumferential fins include inwardly tapered sidesurfaces.
 21. The polyaxial bone fixation assembly of claim 12, whereinthe plurality of non-circumferential fins are each integrally connectedto, and protruding from, an inner surface of the at least one opening orthe head portion of the fastener.
 22. The polyaxial bone fixationassembly of claim 12, wherein the plurality of non-circumferential finseach have a tapered top surface extending to a terminal end of the fin.23. The polyaxial bone fixation assembly of claim 12, wherein theplurality of non-circumferential fins are deflectable so that each ofthe plurality of non-circumferential fins are interposed between thethreads when the at least one fastener is inserted into the at least oneopening.
 24. The polyaxial bone fixation assembly of claim 12, whereinthe plurality of non-circumferential fins are deformable so that each ofthe plurality of non-circumferential fins are interposed between thethreads when the at least one fastener is inserted into the at least oneopening.